Add power on state for BlitzWolf Tuya plugs

[TheJulianJES]

See #605 (comment)

This is tested and working.

This adds the option to change the default power on state for the BlitzWolf Tuya plugs.
I don't know of any other Tuya plugs that also support this. That's one of the reasons I didn't move OnOffRestorePowerCluster and PowerOnState in the __init__.py file in the Tuya directory.
The second reason is that it doesn't look like this plugs needs any Tuya-specific handling (and there is already a TuyaManufacturerClusterOnOff in tuya\__init.py__.
I can move (and rename?) the PowerOnState and OnOffRestorePowerCluster if that would be better.

Also, manufacturer_attributes cannot be used in the OnOffRestorePowerCluster.

[codecov-io]

Codecov Report

Merging #742 (3f0a49f) into dev (4f14ef0) will increase coverage by 0.07%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##              dev     #742      +/-   ##
==========================================
+ Coverage   82.95%   83.02%   +0.07%     
==========================================
  Files         176      177       +1     
  Lines        3931     3948      +17     
==========================================
+ Hits         3261     3278      +17     
  Misses        670      670              

Impacted Files	Coverage Δ
zhaquirks/tuya/plug.py	100.00% <100.00%> (ø)

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[coveralls]

Pull Request Test Coverage Report for Build 505906587

• 17 of 17 (100.0%) changed or added relevant lines in 1 file are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+0.07%) to 83.029%

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Totals
Change from base Build 503912949:	0.07%
Covered Lines:	3278
Relevant Lines:	3948

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💛 - Coveralls